As a synthesis method for carbonyl fluoride, a method of directly fluorinating carbon monoxide with fluorine by a flow method, is known (Non-Patent Document 1). However, to carry out this reaction, there has been a danger of explosion or a decrease in the reaction yield of carbonyl fluoride due to a side reaction, and it has been necessary to add an inert gas such as N2, He, Ne or Ar to the reaction system in order to avoid vigorous heat generation (Patent Document 1).
In such a method of diluting carbon monoxide and fluorine as the stating material gases with an inert gas, it is preferred to carry out the dilution so that the concentration of COF2 will be at most 50% at the outlet of the reactor. After the reaction by this method, obtained COF2 is required to be purified, and as such a purification method, distillation purification or a method of cooling it to a temperature lower than the melting point (−111° C.) of COF2 for solidification, followed by collection, is conceivable.
However, the method of solidifying COF2, followed by collection, is not suitable as an industrial production process from the viewpoint of costs for the extremely low temperature cooling medium such as liquid nitrogen or from the viewpoint of a decrease in the overall heat transfer coefficient with the cooling surface along the progress in the solidification and collection of COF2 in the solidification/collection apparatus. On the other hand, in the method by distillation purification, COF2 (boiling point under atmosphere pressure: −85° C.) is liquefied by condensation to separate the above inert gas having a boiling point lower than COF2, but there is a problem such that COF2 under vapor pressure at the condensation temperature (e.g. from −70° C. to 20° C.) will be lost as accompanied with the above inert gas, whereby the yield of COF2 will be low.
Patent Document 1: JP-A-2003-267712
Non-Patent Document 1: Handbook of preparative inorganic chemistry I, p. 206, 2nd ed., Georg Brauer, ed., Academic Press, New York, 1965